The invention is based on a pump/nozzle unit for fuel injection systems wherein the pump piston is tappet actuated and provided with a regulating sleeve, guide bushing and control lever arm. A pump/nozzle unit of this type is already known (U.S. Pat. No. 2,144,862), in which the piston injection pump and the injection nozzle are combined in a common pump housing into a unit mounted on the cylinder head of the internal combustion engine.
To attain a change in the effective supply stroke or supply quantity, the pump piston, which is actuatable by the engine camshaft via a drive tappet counter to the force of a tappet spring and is provided with at least one oblique control edge, is rotatable by means of a regulating sleeve, disposed coaxially with it and permitting a stroke movement of the pump piston yet carrying the pump piston along with it in the direction of rotation, and by a governor rod engaging this sleeve and embodied as a supply quantity adjusting member. The regulating sleeve is inserted into a recess countersunk in the pump housing beginning at an end face on the drive side, and it is fixed in the axial direction in its installed position by a guide bushing, or by a disc secured by means of this bushing. The drive tappet is received and guided in a sleeve-like guide part of the guide bushing, which is secured in the pump housing via a threaded flange, the diameter of which is larger than that of the rest of the guide part and which is screwed into an internal thread in an enlarged part of the recess in the pump housing.
Because of the thread length necessitated for the sake of strength, and the given structural length of the tappet spring, this threaded securing of the guide bushing results in a correspondingly long structural length of the complete pump/nozzle unit. Moreover, the threaded connection of the components to one another is still incapable of preventing axial misalignments between the drive tappet and the pump piston. Furthermore, the guide bushing can be removed only after the tappet spring has been removed.
A related invention is currently pending to the same inventors under application Ser. No. 630,908, filed July 13, 1984.